Diaphragm pulsating apparatus for paper mill and pulp mill screens



Jan. 30, 1945.- pusT 2,368,291

DIAPHRAGM PULSATING APPARATUS'FOR PAPERMILL AND PULP MILL SCREENS Filed April 1, 1942 :s Sheets-Sheet 1 is Z 12 16 Jan. 30, 1945. DUSTAN 2,368,291

DIAPHRAGM PULSATING APPARATUS FOR PAPER MILL AND PULP MILL S CREENS Filed April 1, 1942 I5 Sheets-Sheet 2 Jan. so, 1945. Y F DUSTAN 2,368,291

DIAPHRAGM PULSATING APPARATUS FOR PAPER MILL AND PULP MILL SCREENS Filed April 1, 1942 s Sheets-Sheet 3 Fig.4

Patented Jan. 30, 1945 UNITED STATES PATENT OFFICE DIAPHRAGM PULSATING APPARATUS FOR PAPER NULL AND PULP MILL SCREENS Frank Dustan, Fitchburg, Mass, assignor, by mesne assignments, to National Lead Company, New York, N. Y., a corporation of New Jersey Claims.

The present invention relates to apparatus for pulsating the diaphragms of flat pulp mill and paper mill screens.

In flat screens, the stock is introduced to the screen vat and flows over perforated or slotted screen plates. Below the plates are diaphragm which are vibrated to produce alternate suction v and pressure in the chamber between the plates which may have become lodged on the plates.

The diaphragms are pulsated at a high rate, frequently 800 or even more pulsations per minute.

The usual construction uses mechanical means in the form of cams, eccentrics or cranks for operating the diaphragms. Since the forces involved are very large, the moving parts must be rigidly constructed and mounted on heavy underframing. There is considerable trouble in maintaining alignment of the shafts and bearings. A moreserious difficulty is that no protection is provided against damage in case of clogging of the plates; in such a case, the plates deflect excessively and may. even be loosened from their fastenings. A particularly serious condition results if the chamber between plate and diaphragm becomes completely flooded through improper supervision, in which case, if the plates are not actually torn from their fastenings, the drivin mechanism may. be thrown seriously out of alignment.

The principal object of the present invention is to provide a diaphragm pulsating apparatus operating hydraulically and having .provision for limiting the forces applied to the diaphragms to permit normal operation under favorable screening conditions and to ,prevent damage to With these and other objects in view, as will claims.

In the accompanying drawings, Fig. 1 is a side elevation of so much of a pulp screen as is necessary for an understanding of the present invention; Fig. 2 is an elevation, partly in section, on line 22 of Fig. 1, and with parts broken away; Fig. 3 is a detail view of the preferred form of screen; Fig. 4 is a view similar to Fig. 1 but on an enlarged'scale to illustrate details of the operating devices; and Fig. 5 is a detail view of one of the stroke adjusting collars.

The screen shown in the drawings comprises a vat 6, into which stock is introduced at one end in the usual fashion. .The vatis provided with screen plates 8 of any suitable type, preferably as shown in my Reissue Patent No. 20,533, reissued October 19, 1937. The screen plates are arranged in pairs, according to usual procedure, and are mounted on supports Ill and I2. Below each pair of plates is a rubber diaphragm l4, suitably secured at its edges to the supports l0 and the frame of the vat. The space between the plates 8 and the diaphragms l4 constitutes a diaphragm chamber I6, which is provided at its end with an outlet 3 connected in the usual manner to the outlet tube 20.

Each diaphragm is secured between 'a. thin metal upper plate 22 and a heavy lower metal frame 24. Connections are made to the frame 24 to provide for pulsating the diaphragm up -and down under the action of the hydraulic means later to be described.

Secured to the lower frame 24 is a hollow cylindrical guide member 26 having at its upper end a flange 28 which is bolted to the frame 24. The guide 26 reciprocates in a bearing member 30 secured between channels 32 which extend across the under-side of the frame and form a part of the supporting structure thereof. As shown in Fig. 2, the bearing 30 has an upper flanged bushing 34 and a lower flanged bushing 36, within which the guide 26 slides.

The flange 28 is provided with a shoulder 38, serving as an abutment to limit the downward motion of the guide. At its lower end the guide is provided with a bolted flange 40, serving to limit the upward movement of the guide. In

order to adjust the stroke of the diaphragm,

thin collars or shims 42 and 44 may be used, the upper collar 42 overlying the flange of the bushing 34 and the lower collar 44 being carried by the flange 40. As shown in Fig. 2, the diaphragm is in its mid-stroke position. Preferably, the collars i2 and M are of the same thickness in order that the stroke of the diaphragm may be equal on both sides of the mid-stroke position v The bearing member 38 is provided with skirt portions 46 extending below the parts previously described and carrying at the bottom a head I! having a stuiiing box 58. A small hydraulic cylinder 52 is secured to the head 48. The cylinder has a piston 54 connected by a rod 88 which through the stufllng box to the member ll at the bottom of the diaphragm guide cylinder. A bydraulic supply tube 88 is connected into the head 48 above the piston 54, and a lower tube 82 is connected to the cylinder head 88 at the bottom of the cylinder. As clearly shown in Fig. 1, one hydraulic cylinder 52 is provided for each diaphrasm.

The diaphragm is pulsated by applying hydraulic pressure alternately through the pipes 50 and 62. The hydraulic system for supplying the cylinders 52 comprises, as shown in Fig. 1, a hydraulic pump 68' driven by a motor 68; The pump has an inlet pipe 88 leading from a reservoir In of oil or other suitable liquid. The outlet of the pump is connected by a pipe 12 to a main pressure line 13 through a relief valve '14 having a discharge pipe 18 to return excess liquid to the reservoir. The system is provided with a, main return line 18 which parallels the main pressure line 13. As shown in P18. 1, the lines run under the screen frame adjacent to the cylinders.

For each hydraulic cylinder, a branch pressure line 80 is connected to the main line I8 and leads through a check-valve 82 to a four-way control valve 84, to which are connected the tubes 60 and 82 leading to the top and bottom of the hydraulic cylinder 52. A branch return line 88 runs from each four-way valve to the main return line 18.

The four-way valves 86 are of well-known construction and need not be described in detail. It is suflicient to note that when the operating rod 88 of the four-way valve is in one position,

operate the diaphragm. Preferably the pump is of the constant-volume type. Consequently, the relief valve 14 will continually operate to discharge some oil back to the reservoir through the relief line 18; Under normal conditions a fairly constant volume of oil will flow through the discharge pipe 18 because of the sta gered operation of the diaphragms. The relief valve is set to maintain in the pressure line 13 a pressure Just suillcient to pulsate the diaphragm through the normal stroke under favorable screening conditions. Ifunfavorable conditions start to develop, as by clogging of a pair of plates or flooding of a diaphragm chamber, the pressure in line 18 will not be suflicient to move the diaphragm through its full stroke against the added resistance caused thereby; consequently, the stroke of the diaphragm will be reduced or, in the case of a completely flooded air chamber, will stop altogether. The reduced amount of oil consumed by cylinder 52, under this condition, will cause an increase of flow through the discharge line 18 from relief valve ll. Thus, the relief valve prevents any overload from being imposed upon the diaphragm and the actuating mechanism, and the entire structure is protected from the excessive racking which is incident to the existing mechanically operated screen frames under similar condi- .ferred form, and may, if desired, be connected to operate any suitable alarm. Since the relief flow a is sensibly constant under normal operating concated at the desired pulsation frequency of the diaphragm, pressure is alternately applied to the top and bottom of the piston 54. eating action of the four-way valve is accomplished by an eccentric drive 98 connected to the -rod 88 by a connecting rod 82 and operated by a The reciprocontinuously rotating shaft 84. As shown in Fig.

a-small amount of power, namely, that necessary to operate the control valves. The eccentrics II are angularly displaced with respect to one another so that the pulsations of the several diaphragms are staggered after the manner of the firing order in an internal combustion engine,

thus preventing excessive vibrations from developing in the structure.

In operation, the pump 84 is designed ior a delivery slightly in excess of that required to ditions, the warning device is sensitive to an immediate change of conditions such as would be occasioned by limitation of the movement of even a single diaphragm.

As heretofore noted, the spacing collars or shims l2 and 44 are changeable to allow for different diaphragm strokes. To facilitate the change, each, collar is preferably made in split form as shown in Fig. 5, the two halves of the collar being secured together after assembly about the guide 28 by shouldered pins M8 in homes ill and held inplaceby cotter-pins I".

It is customary to operate at varying stroke lengths and frequencies for different grades of stock. In general, the longer the stroke the lower the frequency. Hence, when the stroke is changed by inserting collars of different thickness, the

frequency will be varied'by adjusting the speed of the eccentric drive shaft 84. The most satisfactory conditions have been found to obtain wheuthe stroke and frequency are inversely proportional; or at least approximately so. For example, the machine may be operated at 800 strokes per minute with a stroke of in., 533 strokes per minute with a stroke of in., or 400 strokes per minute with a stroke of in. Thus, when the spacing "collars are changed, a corresponding changeis made in the variable-speed drive Ill. Under such conditions, the oil consumption of the diaphragm operating cylinders 82 is substantially constant, that is, slightly less than the delivery of the constant volume type pump 8!; hence no adjustments thereof are necessary and the meter It! stands ready at all times to warn of any increase of discharge from the relief valve id arising from the reduced motion or stoppage of any one or more of the diap in the preferred embodiment of the invention has been illlustrated and described, it will be understood that the invention is not limited to such preferred embodiment, but may be varied Within the scope of the appended claims.

Having thus described my invention, I claim:

1. in diaphragm pulsating apparatus for flat mill. and pulp mill screens, the combinawith a reciprocating guide connected with a hragm, 'a bearing in which the guide rete-s, a pump, pressure-relief means for in, piston connected to the guide a conpaper mill and pulp mill screens, the combination with a plurality of reciprocating guide members individually connected with a diaphragm, of hydraulic means for reciprocating the diaphragms individual hydraulic motors connected with the guide members, a control valve for each motor disposed immediately adjacent thereto, an eccentric device for operating each control valve, and a common drive for the several eccentric devices, the eccentrics being angularly displaced with respect to one another to stagger the operation of the diaphragms.

3. Diaphragm pulsating apparatus for flat paper mill and pulp mill screens comprising, in combination with a plurality of diaphragms, individual hydraulic motors associated therewith, a source of fluid pressure, individual control means connected with each hydraulic motor in close proximity thereto for controlling the delivery oi fluid from the source to each motor, and individual driving connections from the motors to the respective diaphragms, said driving connections including individual abutment means to provide positive individual adjustment of the stroke of each diaphragm independently of fluid pressure and frequency.

a. Diaphragm pulsating apparatus for flat paper mill and pulp mill screens comprising, in combination with a plurality of diaphragms, individual hydraulic motors associated therewith, a source of fluid pressure, individual control means connected with each hydraulic motor in close proximity thereto for controlling the delivery of fluid from the source to each motor, individual driving connections including reciprocating guides from'the motors to the respective diaphragms, and spacing collars surrounding the guides and forming individual abutment means to provide positive individual adjustment of the stroke of each diaphragm independently of fluid pressure and frequency.

5. Diaphragm pulsating apparatus for fiat paper mill and pulp mill screens comprising, in combination with a plurality of diaphragms, in-

dividual hydraulic motors associated therewith,

a source or fluid pressure, a control valve for each motor disposed immediately adjacent thereto, individual driving connections from the motors to the respective diaphragms, said driving connections including individual abutment means to provide positive individual adjustment of the stroke of each diaphragm independently of fluid pressure and frequency, and means for controlling operation of the valves in a timed relatlon to stagger the pulsations of the several diaphragms.

FRANK DUSTAN. 

